Core samples are obtained through core drilling operations. Core drilling is typically conducted with a core drill comprising outer and inner tubes, the inner tube being part of a core barrel assembly. A hollow drill bit is attached to the outer tube assembly, so that rotational torque applied to the outer tube assembly is transmitted to the drill bit. A core is generated during the drilling operation, with the core progressively extending along the inner tube assembly as drilling progresses. When a core sample is acquired, the core within the inner tube assembly is fractured. The core barrel assembly, and the fractured core sample contained therein, are then retrieved from within the drill hole, typically by way of a retrieval cable lowered down the drill hole and attached to the core barrel assembly. Once the core barrel assembly has been removed from the bore, the core sample can be removed and subjected to analysis.
Typically, the core barrel assembly is secured in position inside the outer tube by the means of latches that extend substantially radially outwardly from the core barrel assembly. The latches are received inside notches or grooves formed into the inner surface of the outer tube and are selectively retractable for locking and unlocking the core barrel assembly to and from the outer tube. However, currently used latches may become disengaged from the outer tube assembly during the drilling process because of vibrations produced during this process. When drilling upholes, a mislatch represents a danger since the core barrel assembly can come back to the driller's working area. In addition, the core barrel assembly may be damaged if this occurs.
Also, in embodiments in which drilling is performed horizontally or upward, allowing the fluid to reach the end of the bore before the core barrel assembly is positioned nearby could lead to problems as debris could be dislodged and projected with relatively large force through the bore.
Against this background, there exists a need in the industry to provide an improved core barrel assembly.
An object of the present invention is therefore to provide an improved core barrel assembly.